1. Field of the Invention
The present invention relates to a time division multiplex remote control system and, more particularly, relates to an interruption handling system capable of rapidly handling an interruption when a supervisory input in a terminal causes a change.
2. Description of the Prior Art
FIG. 1 shows a schematic block diagram showing the whole of this type of a time division multiplex remote control system. Such a remote control system includes a central controller 1 and a plurality of terminals 2 having the respective inherent addresses connected to a signal line 3. A transmission signal including inherent address data is transmitted from the central controller 1 so that a terminal 2 corresponding to the inherent address is accessed, and the communication of data such as control data and supervisory data has been made between the central controller 1 and the accessed terminal 2. For example, in a modern building, terminals 2, 2, . . . are provided in each of several rooms, respectively, the terminals 2, 2, . . . applying control information to an object to be supervised, such as a lamp and a wall type switch in each room and also supervising a change of a supervisory input from each of the objects to be supervised. For example, assuming that the object to be supervised is a wall type switch and the switching of the lamp is made by an on/off of the wall type switch, the change from the off to the on in the wall type switch is detected as a change of a supervisory input by the terminal 2 when the wall type switch is rendered on for the purpose of lighting. The data as to the change of the supervisory input, which is supervisory data, is returned to the central controller 1, as a reply signal when the corresponding terminal 2 is accessed through polling from the central controller. The central controller 1 receives the supervisory data and then sends to the terminal 2 control data necessary for lighting a corresponding lamp. The terminal 2 accepts the control data and lights the lamp.
FIG. 2 shows an example of a format of a transmission signal used in a conventional time division multiplex remote control system. The transmission signal includes a start signal or a field of start signal ST, an address signal or an address signal region AD for transmitting address data of a terminal, a control signal or a control signal region CTR for transmitting control data, a reply signal standing-by period defining signal or a reply signal standing-by period defining signal region RW for defining a time period for receiving a reply signal from the addressed terminal. The transmission signal is in a form of bipolar signal which is pulse-width modulated.
Now, referring to FIGS. 1 and 2, an operation of the conventional time division multiplex remote control system will be briefly described. First, the central controller 1 sequentially and cyclically accesses the terminals 2. To this end, each of the terminals is sequently polled by sequentially changing the address data included in the transmission signal shown in FIG. 2. If and when the terminal 2 receives a transmission signal including address data coinciding with its own inherent address, the terminal 2 accepts the control data included in the transmission signal and outputs the control output CS to control a load associated with the terminal and also sends out to the central controller 1 supervisory data, as a reply signal, based on a supervisory input SS during the period set by a reply signal standing-by period defining signal RW.
As described in the foregoing, since, in this type of a conventional time division multiplex remote control system, each of the terminals 2 is sequentially accessed, the time necessary for accessing all of the terminals 2, 2, . . . becomes longer as the number of the terminals is increased. Accordingly, even if a change of the supervisory input SS occurs immediately after a certain terminal 2 is polled, the terminal 2 will be responsive at the time of the next polling after all of the remaining terminals are polled, which means that the rate of the response is very slow. For example, by way of an example of the above described wall type switch, non-practical situation occurs where a lamp is lighted 5 to 10 seconds later even if a switch is rendered on for the purpose of lighting the lamp. In addition, assuming that an object to be supervised is a smoke sensing apparatus, for example, even if the smoke sensing apparatus senses smoke and the terminal 2 detects the change of the supervisory input SS, the response thereto possibly becomes slower due to the order of the polling, which is, of course, not practical.
Furthermore, since all of the terminals are cyclically accessed, the frequency of accessing a single terminal 2 is necessarily decreased if the number of the terminals 2 is increased.